1. Field of the Invention
This invention relates to the use of phenol-aldehyde-amine resins to produce rigid and semiflexible polyurethane foams. The rigid and semiflexible foams produced according to this invention have, relative to similar foams produced without such resins, increased resistance to burning as well as to crumbling (friability).
2. Description of the Prior Art
Rigid polyurethane foams find commercial utility in varied areas ranging from high density molding applications such as in the production of decorative furniture replacements for wood to appliance and other pour-in-place insulation applications to various spray applications. Semiflexible polyurethane foams find commercial utility in automotive interior trim applications. In addition to requiring certain desirable physical properties relative to density, compression strength, friability, etc., such commercial applications require that the rigid and semiflexible foams have as low a degree of combustibility as possible.
Currently, relatively low degrees of combustibility are achieved commercially by incorporating into the rigid and semiflexible foam formulations various flame retardants such as non-reactive chlorinated phosphonate esters or reactive trichlorobutylene oxide based polyether polyols. However, even lower degrees of combustibilities are desirable.
U.S. Pat. No. 4,107,106 is concerned with elastomers (flexible and semiflexible) which are useful as energy absorbing components in automobile bumpers, crash pads, packaging, and the like. That patent utilizes a phenol-aldehyde-amine resin component as a curative to make its polyurethanes. However, the afore-mentioned patent teaches that the phenol-aldehyde-amine resin is utilized in conjunction with, and preferably premixed with, a diol curative. The diol curative of the patent, in combination with the resin, is taught to affect the strain rate sensitivity of the polyurethane elastomers prepared according to the process of the patent. U.S. Pat. No. 4,107,106 does not disclose or suggest that the phenol-aldehyde-amine resin lowers combustibility. In fact, no flame retardants of any kind are identified as such in that patent.